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CHAPTER 13 UART
Table 13.4-2 Functions of Bits for Mode Register (SMR0/SMR1)
Bit name
Function
bit7
bit6
MD1 and MD0:
Operation mode
selection bits
These bits select an operation mode.
Note:
Operation mode 1 (multiprocessor mode) can be used only from the master
system during master-slave communication. UART cannot be used from the
slave system because it has no address/data detection function during
reception.
bit5
bit4
bit3
CS2 to CS0:
Clock selection bits
This bit selects a baud rate clock source. When the dedicated baud rate
generator is selected, the baud rate is determined at the same time.
When the dedicated baud rate generator is selected, eight baud rates can be
selected: 6 types for the dedicated baud rate generator selected, 1 type for
the internal timer selected, and 1 type for the external clock selected.
Clock input can be selected from external clocks (SCK0/SCK1 pin input), the
internal clock (16-bit reload timer), and the dedicated baud rate generator.
bit2
-:
Undefined bit
When this bit is read, the value is undefined.
The value set to this bit does not affect operation.
bit1
SCKE:
Serial clock output
enable bit
This bit controls the serial clock input-output ports.
When this bit is 0, the P40/SCK0 and P62/SCK1 pins operate as input-
output ports or serial clock input pins. When this bit is 1, the pins operate as
serial clock output pins.
Note:
- To use the P40/SCK0 and P62/SCK1 pins as serial clock input (SCKE="0")
pins, set them as input pins. Also, select an external clock (SMR0/SMR1:
CS2 to CS0="111B") using the clock setting bits.
- To use the P40/SCO0 and P62/SCO1 pins as serial clock output
(SCKE="1") pins, select the dedicated baud rate generator (SMR0/SMR1:
CS2 to CS0="000B" to "101B") or internal clock (SMR0/SMR1: CS2 to
CS0="110B").
Reference:
When the SCK0/1 pin is assigned to serial clock output (SCKE=1), it
functions as the serial clock output pin regardless of the status of the input-
output ports.
bit0
SOE:
Serial data output
enable bit
This bit enables the output of serial data.
When this bit "0", the P37/SOT0, P61/SOT1 pins operate as an I/O port.
When this bit "1", the P37/SOT0, P61/SOT1 pins operate as a serial data
output pin.
Reference:
When the serial data output (SOE="1") is selected, the pins operate as a
serial data output pin regardless of the state of the I/O port.